Testing the global-slowing hypothesis: are alcohol's effects on human performance process-specific or task-general?

Acute alcohol effects on impulsive choice in adolescents

BACKGROUND

Neurodevelopmental and alcohol-induced changes in decision-making have been proposed to critically influence impulsive behaviour in adolescents.

OBJECTIVE

This study tested the influence of acute alcohol administration on impulsive choice in adolescents.

METHODS

Fifty-four males aged 18-19 years were tested in a single-blind placebo-controlled cross-over design. During alcohol administration (infusion resulting in an arterial blood alcohol concentration of 80 mg%) and placebo condition (saline infusion), participants performed a task battery providing estimates of delay discounting, probability discounting for gains, for losses and loss aversion, and also rated subjectively experienced alcohol effects. Additionally, baseline alcohol consumption (Alcohol Use Disorders Identification Test, blood phosphatidylethanol levels), motives (Drinking Motive Questionnaire, Alcohol Expectancy Questionnaire and Obsessive Compulsive Drinking Scale), family history and self-report measures of impulsivity (Barratt Impulsiveness Scale, Substance Use Risk Profile Scale) were provided.

RESULTS

No overall effects of treatment on choice behaviour were found. However, individual differences were observed. In the alcohol condition, more impulsive choice tendencies for delay discounting were associated with higher subjectively experienced alcohol effects. Further, higher risk aversion for probabilistic gains and higher loss aversion during alcohol condition were related to higher levels of real-life alcohol consumption and a family history of alcohol problems, respectively. Finally, the time to make a decision was substantially shortened for choices involving negative prospects.

CONCLUSIONS

Contrary to common beliefs, acute alcohol intoxication did not generally incite impulsive decision-making. It rather appears that alcohol-induced behavioural changes in adolescents vary considerably depending on prior experiences and subjective effects of alcohol.

The effects of breath alcohol concentration on postural control

BACKGROUND

Two of the 3 standardized field sobriety tests that U.S. law enforcement uses at roadside checks have a postural equilibrium component to them. Those tests have been validated to detect impairment caused by blood alcohol concentrations (BACs) of 0.08 g/dL or above. Many medical and traffic safety associations support a lower limit, and one state, Utah, has passed a law to lower the limit to 0.05 g/dL. Many studies have examined the effects of alcohol on postural control (of which postural equilibrium is a component), with a consensus emerging that impairment is usually found at BACs greater than 0.06 g/dL. Most of these studies, however, had a relatively small number of subjects, usually between 10 and 30. The current study collected data from a much larger sample.

OBJECTIVE

The objective of this study was to provide additional evidence that posture control is negatively affected at BACs greater than 0.06 g/dL or breath alcohol concentrations (BrACs) of 0.06 g/210 L.

METHOD

This was a between-subjects study, with BrAC group as the independent variable (5 levels: 0.00, 0.04, 0.06, 0.08, and 0.10 g/210 L); 4 measures of postural control as the dependent variables; and age, height, and weight as the covariates. Posture control was measured with a force-sensing platform connected to a computer. The feet's center of pressure (CoP) on the platform was recorded and the corresponding movement of the body in the anterior-posterior and lateral planes was derived. Participants (N = 96) were randomly assigned to one of the BrAC groups. Positive BrAC groups were compared to the zero BrAC group. Data were examined with hierarchical multiple regression.

RESULTS

Adjusted for age, height, and weight, the main effect of lateral CoP with eyes open was not statistically significant. There was a statistically significant main effect of alcohol on anterior-posterior CoP excursion with eyes open and with eyes closed and lateral CoP excursion with eyes closed. For all 3 of those variables, only BrACs of 0.08 and 0.10 g/210 L produced differences against zero BrAC. Although the main effect of alcohol on Lateral CoP Excursion with eyes open was not statistically significant, the contrasts between 0 and 0.08 and 0 and 0.10 g/210L BrAC were in the hypothesized direction.

CONCLUSION

The current study did not directly address the issue of whether the sobriety tests are sensitive to BrACs of 0.05 g/210 L or above; rather, it provides additional evidence that postural control, one of the components of those tests, is relatively unaffected by BrACs lower than 0.08 g/210 L. Additional research is needed on the diagnostic characteristics of the sobriety tests at BrACs lower than 0.08 g/210 L.

High-dose alcohol intoxication differentially modulates cognitive subprocesses involved in response inhibition

Aside from well-known physiological effects, high-dose alcohol intoxication (a.k.a. binge drinking) can lead to aversive social and legal consequences because response inhibition is usually compromised under the influence of alcohol. Although the behavioral aspects of this phenomenon were reported on extensively, the underlying neurophysiological mechanisms mediating this disinhibition are unclear. To close this gap, we used both behavioral and neurophysiological measures (event-related potentials, ERPs) to investigate which subprocesses of response inhibition are altered under the influence of high-dose alcohol intoxication. Using a within-subject design, we asked young healthy participants (n = 27) to complete a GO/NOGO task once sober and once intoxicated (approximately 1.2‰). During intoxication, high-dose alcohol effects were highest in a condition where the participants could not rely on automated stimulus-response mapping processes during response inhibition. In this context, the NOGO-P3 (ERP), that likely depends on dopaminergic signaling within mesocorticolimbic pathways and is thought to reflect motor inhibition and/or the evaluation of inhibitory processes, was altered in the intoxicated state. In contrast to this, the N2 component, which largely depends on nigrostriatal dopamine pathways and is thought to reflect inhibition on a pre-motor level, was not altered. Based on these results, we demonstrate that alcohol-induced changes of dopaminergic neurotransmission do not exert a global effect on response inhibition. Instead, changes are highly subprocess-specific and seem to mainly target mesocorticolimbic pathways that contribute to motor inhibition and the evaluation of such.

The influence of acute and chronic alcohol consumption on response time distribution in adolescent rhesus macaques

BACKGROUND

Analysis of the distribution of reaction times (RTs) in behavioral tasks can illustrate differences attributable to changes in attention, even when no change in mean RT is observed. Detrimental attentional effects of both acute and chronic exposure to alcohol may therefore be revealed by fitting RT data to an ex-Gaussian probability density function which identifies the proportion of long-RT responses.

METHODS

Adolescent male rhesus macaques completed a 5-choice serial reaction time task (5CSRT) after acute alcohol consumption (up to 0.0, 1.0 and 1.5 g/kg). Monkeys were next divided into chronic alcohol (N = 5) and control groups (N = 5); the experimental group consumed 1.5-3.0 g/kg alcohol for 200 drinking sessions. Unintoxicated performance in the 5CSRT task was determined systematically across the study period and the effect of acute alcohol was redetermined after the 180th drinking session. The effect of extended abstinence from chronic alcohol was determined across 90 days.

RESULTS

Acute alcohol exposure dose-dependently reduced the probability of longer RT responses without changing the mean or the standard deviation of the RT distribution. The RT distribution of control monkeys tightened across 10 months whereas that of the chronic alcohol group was unchanged. Discontinuation from chronic alcohol increased the probability of long RT responses with a difference from control animals observed after 30 days of discontinuation.

CONCLUSIONS

Alcohol consumption selectively affected attention as reflected in the probability of long RT responses. Acute alcohol consumption focused attention, chronic alcohol consumption impaired the maturation of attention across the study period and alcohol discontinuation impaired attention.

Functional biomarkers for the acute effects of alcohol on the central nervous system in healthy volunteers

The central nervous system (CNS) effects of acute alcohol administration have been frequently assessed. Such studies often use a wide range of methods to study each of these effects. Unfortunately, the sensitivity of these tests has not completely been ascertained. A literature search was performed to recognize the most useful tests (or biomarkers) for identifying the acute CNS effects of alcohol in healthy volunteers. All tests were grouped in clusters and functional domains. Afterwards, the effect of alcohol administration on these tests was scored as improvement, impairment or as no effect. Furthermore, dose-response relationships were established. A total number of 218 studies, describing 342 different tests (or test variants) were evaluated. Alcohol affected a wide range of CNS domains. Divided attention, focused attention, visuo-motor control and scales of feeling high and of subjective drug effects were identified as the most sensitive functional biomarkers for the acute CNS effects of alcohol. The large number of CNS tests that are used to determine the effects of alcohol interferes with the identification of the most sensitive ones and of drug-response relationships. Our results may be helpful in selecting rational biomarkers for studies investigating the acute CNS effects of alcohol or for future alcohol- interaction studies.

Attention to social threat as a vulnerability to the development of comorbid social anxiety disorder and alcohol use disorders: an avoidance-coping cognitive model

Despite the frequent comorbidity of social anxiety disorder and alcohol use disorders, no theoretical model currently exists to explain the specific mechanisms underlying the comorbidity between these two disorders. An integration of existing theoretical models and empirical evidence across the social anxiety and alcohol use literatures is presented as the Avoidance-Coping Cognitive Model, which proposes that socially anxious individuals may be particularly vulnerable to the anxiolytic effects of alcohol through reductions in attention biases to social threat. The disproportionate reduction in anxiety may then make alcohol an attractive method of avoidance coping. Gaps in the empirical literature are reviewed in light of this model as future directions are suggested.

Comparing the Effects of Light Alcohol Consumption on Human Response to Auditory and Visual Stimuli

The purpose of this study is to examine the effects of various levels of alcohol consumption on human response to auditory and visual stimuli in terms of reaction time, movement time, total reaction time, and error rate. Placebo level and three low-level alcohol doses were randomly assigned to 20 male university student volunteers. 30 min. after consuming the alcohol or placebo, participants responded to either auditory or visual stimuli. Total reaction time increased significantly at the mid-low dose of alcohol (0.3 g/kg). For alcohol doses less than .5 g/kg, the change in total reaction time was confined to reaction time, i.e., the processing time between onset of stimulus and onset of movement. Effects of alcohol were significantly more pronounced in the choice-type tests. Notably, the effects of alcohol on total reaction time and error rate were significant for auditory but not visual stimuli.

Alcohol and estrogen replacement therapy in postmenopausal women. Direct and mediated effects on cognitive component processes

The literature remains contentious regarding the separate and combined effects of moderate drinking and estrogen replacement therapy (ERT) on cognition. In the current study, the authors sought to disentangle the predictive utility of alcohol use, ERT and their interaction on the episodic and semantic memory stores of postmenopausal women. It was predicted that relationships between moderate drinking, ERT and cognition would be attenuated by demographic and health-related factors. Postmenopausal women (n = 298) completed a battery of cognitive tests designed to assess speed and accuracy of episodic and knowledge-based cognitive processing. Potentially confounding variables were categorized and tested as mediators in hierarchical regression analyses. Moderate drinking was a weak predictor of episodic availability prior to removal of potential mediators. ERT use was a significant predictor of episodic and knowledge-based availability; no mediators were identified. Alcohol moderated ERT, as a combined alcohol/ERT variable was shown to be related to cognition. Neither moderate drinking nor ERT use was associated with cognitive speed. These findings suggest that positive relationships between alcohol and cognition are likely mediated by other variables, and should not be regarded as a benefit of drinking. Further, results support ERT as a predictor of knowledge-based and episodic availability, independent of mood stabilization or socioeconomic influences. Finally, alcohol and ERT appear to interact to impact both episodic and knowledge-based performance.

The stage-specific effect of alcohol on human information processing

RATIONALE

Research on the limits of information processing shows that when a dual task is performed in quick succession, performance on the second task is increasingly degraded as the temporal gap between task 1 and task 2 decreases. The carry-over effect on task 2 is assumed to occur because the central cognitive stage of processing must be completed before the processing of task 2 can begin. This creates a bottleneck when the tasks are performed in close succession, but with longer delays task 2 is no longer affected by task 1.

OBJECTIVES

It was predicted that if alcohol disturbs (slows) the central stage of processing, shorter delays between task 1 and task 2 should reveal more intense disruption in the performance of task 2.

METHODS

Two groups (n=16) of healthy male social drinkers performed a baseline test on a dual task. On each trial, task 1 was followed by task 2 at one of four delays (50, 200, 500, and 1100 ms). The groups then received either 0.65 g alcohol/kg or a placebo and performed the task again.

RESULTS

The RT of the alcohol and placebo groups did not differ on the baseline test. In accord with the hypothesis, the alcohol group performed task 2 more slowly on the treatment test than did the placebo group at the three shortest delays (P<0.02). At the longest delay, the RT of the groups did not differ (P>0.15).

CONCLUSIONS

This pattern of task 2 RTs indicates that a moderate dose of alcohol can significantly impair (slow) the central, cognitive stage of information processing.

The exhaustive additivity displayed by nitrous oxide has implications for cognitive-energetical theory

The cognitive-energetical approach, which relies on the discrete stage model of additive factors logic, asserts that basal energetical mechanisms such as arousal act via particular information processing stages. The anaesthetic gas nitrous oxide (N(2)O) produces additivity at four of the five perceptual and central stages, but its effect on the remaining stage, feature extraction, is unknown. We investigated this stage using 12 subjects who performed a visual oddball experiment in which two levels of stimulus quality, three levels of breathing mixture (air, 25% and N(2)O, 35%) and three levels of stimulus probability were combined factorially. Reaction time (RT) and P300 were collected simultaneously. The RT results showed additivity between N(2)O, stimulus quality and probability. P300 latency also showed additivity between N(2)O and stimulus quality. Since the discrete stage model cannot easily account for the exhaustive additivity displayed by N(2)O on perceptual and central stages, we performed a continuous cascade model simulation to determine whether it is better able to account for this phenomenon. We found that exhaustive additivity could be reproduced by adding a time delay to the activation rate of the first stage, which we interpreted as evidence that N(2)O causes slowing prior to stage processing. To account for these results, we propose a two-tiered energetical model in which a lower GABAergic reticular system (influenced by N(2)O) modulates the activity of upper 'arousal-like' multidimensional ascending thalamocortical systems. The applicability of this model to drugs such as the barbiturates, the benzodiazepines and ethanol, as well as the aging process, is discussed.